A novel Hg2+ fluorescence sensor TPE-TSC based on aggregation-induced emission

Abstract

A fluorescent sensor TPE-TSC with aggregation induced emission (AIE) characteristic is synthesized for detecting Hg²⁺ by attaching thiosemicarbazide (TSC) unit into tetraphenylethylene (TPE) group. TPE-TSC exhibits intense green emission in DMSO/H₂O (V:V?=?1:9) solution with the formation of the aggregation. TPE-TSC shows outstanding fluorescence quenching toward Hg²⁺ over other metal ions due to the formation of complex TPE-TSC/Hg²⁺ with a 2:1 binding ratio. The detection limit of TPE-TSC for Hg²⁺ is 1?×?10^?5 mol·L^?1.     

Naphthalene thiourea derivative based colorimetric and fluorescent dual chemosensor for F− and Cu2+/Hg2+ ions

A structurally simple (Z)-2-(naphthalen-2-ylmethylene)-N-phenylhydrazinecarbothioamide (R1) was used as a colorimetric and fluorescent sensor for both F^?  and Cu²⁺/Hg²⁺ ions. R1 selectively recognised F^?  ions as indicated by colour change from colourless to green. Fluorescence spectral data reveal that R1 is an excellent fluorescence chemosensor for Cu²⁺ ions. Finally, R1 was successfully applied to the bioimaging of Cu²⁺ ions in RAW 264.7 macrophage cells.     

A multichannel thiacalix[4]arene-based fluorescent chemosensor for Zn2+, F− ions and imaging of living cells

Abstract

The fluorescent sensor (3) based on the 1,3-alternate conformation of the thiacalix[4]arene bearing the coumarin fluorophore, appended via an imino group, has been synthesised. Sensing properties were evaluated in terms of a colorimetric and fluorescence sensor for Zn²⁺ and F^?. High selectivity and excellent sensitivity were exhibited, and ‘off-on’ optical behaviour in different media was observed. All changes were visible to the naked eye, whilst the presence of the Zn²⁺ and F^? induces fluorescence enhancement and the formation of a 1:1 complex with 3. In addition, 3 exhibits low cytotoxicity and good cell permeability and can readily be employed for assessing the change of intracellular levels of Zn²⁺ and F^?.     

Optical detection of cyanide by palladium(II)-dithiazolopyridine probe at the parts per billion level

Abstract

The ensemble of 2,6-bis(2-chlorophenyl)dithiazolo[4,5-b:5',4'-e]pyridine 1 with Pd²⁺ ions (1?Pd²⁺) was prepared for the detection of cyanide ions (CN^¯) in 50% aqueous methanol. Among the tested metal ions, only Pd²⁺ sensitively induced the red shift of the absorption bands and the complete decrease of fluorescence emission. The detection limit toward Pd²⁺ was 2?ppb. The ensemble 1?Pd²⁺ selectively and rapidly detected a low concentration of cyanide ions by a colorimetric change (40?ppb) as well as a “turn-on” fluorescent response (5?ppb). Job’s plot revealed the complex formation with 1:1 stoichiometry. The binding and replacement mode of 1?Pd²⁺ and CN^¯ were also confirmed by ¹H NMR titrations and IR analysis. In general, a fast and selective recognition of CN^¯ is reported.     

A new “naked-eye” colorimetric and ratiometric fluorescent sensor for imaging Hg2+ in living cells

A new oligothiophene-based sensor 3 TH for monitoring Hg²⁺ has been designed and synthesized based on the intramolecular charge transfer (ICT) mechanism. The 3 TH shows the significant specificity toward Hg²⁺ through “naked-eye” colorimetric detection as well as via ratiometric fluorescence enhancement response with low detection limit of 62 nM. In addition, sensor 3 TH shows high selectivity and sensitivity for Hg²⁺ with fast response in a suitable pH range. Moreover, the 3 TH-based test strips was used to conveniently detect Hg²⁺ ions in water. Furthermore, considering its good ‘‘turn-on’’ fluorescent sensing behavior and low cell cytotoxicity, 3 TH was successfully applied to detect and image Hg²⁺ in real water samples and living cells, which shows great potentials for application in environmental and biological systems.     

2-(2′-Hydroxyphenyl)-4(3H)-quinazolinone derivatives based fluorescent probes for mercury(II) via an intramolecular proton transfer mechanism

2-(2′,5′-Dihydroxy-phenyl)-4(3H)-quinazolinone (DHPQ), a new fluorescent dye that exhibits excited state intramolecular proton transfer (ESIPT) reaction and possesses good photophysical properties, is synthesised and used as fluorescent probe for detection of Hg²⁺. Mercuric ions can be detected and quantitated by measuring the fluorescent intensity decrease of the probe. The decrease of fluorescence intensity of DHPQ upon the addition of Hg²⁺ was attributed to the blocking of ESIPT reactions of DHPQ and quenching its fluorescence. The analytical performance characteristics of the proposed Hg²⁺ probe were investigated. The probe can be applied to the quantification of Hg²⁺ with a concentration range covering from 8.0?×?10^?7 to 2.0?×?10^?4?mol?L^?1, with a working pH range of 5.5–6.5. It shows excellent selectivity for Hg²⁺ over other transition metal cations. The proposed method was testified for the Hg²⁺ assay in river water samples with satisfying recoveries.     

A new BODIPY-based fluorescent “turn-on” probe for highly selective and rapid detection of mercury ions

A new fluorescent sensor based on the BODIPY fluorophore and the carboxyl-thiol metal bonding receptor for Hg²⁺ was designed and synthesized. The sensor is highly selective for Hg²⁺ (about 630-fold fluorescence enhancement) over relevant competing metal ions, sensitive to ppb levels of Hg²⁺ (with detection limit of 5.7?nM), and fast response toward Hg²⁺ (within 30?s) in aqueous solution.     

A Simple Colorimetric Sensor with High Selectivity for Mercury Cation in Aqueous Solution

Abstract

A simple and sensitive mercapto thiadiazole Schiff-base colorimetric chemosensor 2 was synthesized. It exhibits good selectivity and sensitivity for the mercury cation over other metal cations such as Zn²⁺, Pb²⁺, Cd²⁺, Ni²⁺, Co²⁺, Ag⁺, Ca²⁺, Mg²⁺, and Cr³⁺ in both aqueous solution and on paper-made test kits. The change in color is very easily observed by the naked eye for the presence of Hg²⁺ cation, whereas other metal cations do not induce such a change. The chemosensor 2 showed remarkably anti-interference ability toward other metal cations and the detection limit toward Hg²⁺ was 1.5 × 10^?5 M.

GRAPHICAL ABSTRACT      

基于四丹磺酰胺杯[4]芳烃的汞离子荧光化学传感器

我们方便地合成了上沿修饰四丹磺酰胺基团的杯[4]芳烃衍生物1,发现该化合物在含50％水的乙腈中显示出对汞离子高选择性和灵敏性的识别作用,竞争实验表明多数金属离子对其检测干扰较小。机理研究结果表明荧光萃灭源于由丹磺酰胺基团到汞离子的光致电子转移过程。另外,通过研究1和1-Hg2+的荧光衰减实验,以及对比双丹磺酰胺杯[4]芳烃2和单丹磺酰胺杯[4]芳烃3对汞离子的识别作用,发现化合物1的四丹磺酰胺基团具有很好的预组织和协同作用。化合物1对汞离子的检测限为3.41×10-6 mol·L-1,这可以使1成为一个潜在的汞离子荧光化学传感器。     

Highly selective detection of Hg ion by push–pull-type purine nucleoside-based fluorescent sensor

Highly selective detection of Hg²⁺ ion has been achieved using the push–pull-type purine nucleoside-based fluorescent sensor L1. The sensor L1 incorporating aza-18-crown-6 at C6 position of purine nucleoside, is highly sensitive and selective toward Hg²⁺ ion in CH₃CN–H₂O mixture (92/8, v/v). The detection limit for the fluorescent sensor L1 toward Hg²⁺ ion is 7.8 × 10⁻⁸.     

Fluorescent chemosensor for mercury(II) cations in an aqueous solution based on 4-acetylamino-1, 8-naphthalimide derivative containing the N-phenylazadithia-15-crown-5-ether receptor

The 4-acetylamino-1,8-naphthalimide derivative containing the N-phenylazadithia-15-crown-5-ether fragment in the N-aryl substituent at the imide nitrogen atom of the naphthalimide core was synthesized, and its cation-dependent spectral properties were studied. The resulting compound in the photoexcited state exhibits low-intensity fluorescence due to the process of electron transfer from the N-aryl group to the naphthalimide residue, which is confirmed by the data of quantum chemical calculations performed using the PM6 method. The binding of Hg²⁺ in an aqueous acetate buffer solution at pH 6.0 is accompanied by the formation of a 1: 1 metal—ligand complex in which the electron transfer is suppressed leading to fluorescence enhancement. The observed spectral changes were used for the determination of the stability constant K of the complex (logK = 6.51±0.03). The found limit of Hg²⁺ detection using the synthesized sensor (28 nmol L^?1) is fairly close the maximum permissible concentration for mercury in drinking water. The study of the selectivity of complexation showed that the presence of Cu²⁺, Zn²⁺, Ni²⁺, Pb²⁺ Cd²⁺, Ca²⁺, Mg²⁺, and Fe²⁺ cations did not impede the determination of Hg²⁺. The presented results indicate that the synthesized chemosensor is promising as a selective and highly sensitive fluorescent reagent for Hg²⁺ ions in an aqueous solution.

     

Design of multiple-target chemoprobe: “naked-eye” colorimetric recognition of Fe3+ and off–on fluorogenic detection for Hg2+ and its on-site applications

A novel multiple-target chemoprobe (E)-N′-((9-pentyl-9H-carbazole-3-yl)methylene)thiophene-2-carbohydrazide (CTH) was designed, successfully synthesized and employed for the detection of Hg²⁺ and Fe³⁺ ions as off–on fluorometric and colorimetric responses, respectively, in H₂O/DMF (10/90, v/v, Britton–Robinson buffer, pH 7) medium. The chemoprobe CTH demonstrated high sensitivity towards Hg²⁺ and Fe³⁺, among wide range of competitive cations with low recognition limits of 5.1 nM and 5.89 µM, respectively. The complexes of the chemoprobe CTH were synthesized and characterized by ¹H-NMR titration, FT-IR and MALDI-TOF MS techniques, which confirmed the binding stoichiometries and the possible sensing mechanisms, were suggested based on the hydrolysis reaction of C=N group. The practical utility of the chemoprobe CTH was revealed in quantification of the trace amounts of Hg²⁺ and Fe³⁺ in water samples. Also, a silica-coated test paper was used for the fluorescent monitoring of Hg²⁺, providing a novel approach for the quantitative and on-site detection in real samples. More excitingly, a smartphone application was employed for the visual detection of Fe³⁺ by recognizing the RGB (red/green/blue) of the chemoprobe CTH solution.

Graphical abstract

     

Effect of the Counterion on Light Emission: A Displacement Strategy to Change the Emission Behaviour from Aggregation‐Caused Quenching to Aggregation‐Induced Emission and to Construct Sensitive Fluorescent Sensors for Hg2+ Detection

In this paper, a simple strategy to change the emission behaviour of luminogenic materials was developed. Tetraphenylethene (TPE)‐functionalised benzothiazolium salts with different counteranions (TPEBe?X; X=I^?, ClO₄^? and PF₆^?) were designed and synthesised. All the luminogens show weak red emission in the solution state that originates from intramolecular charge transfer from TPE to the benzothiazolium unit. Whereas aggregate formation enhances the light emission of TPEBe?ClO₄ and TPEBe?PF₆, that of TPEBe?I is quenched, thus demonstrating the phenomena of aggregation‐induced emission and aggregation‐caused quenching. TPEBe?I works as a light‐up fluorescent sensor for Hg²⁺ in aqueous solution with high sensitivity and specificity owing to the elimination of the emission quenching effect of the iodide ion by the formation of HgI₂ as well as the induction in aggregate formation by the complexation of Hg²⁺ with the S atom of the benzothiazolium unit of TPEBe?I. A solid film of TPEBe?I was prepared that can monitor the level of Hg²⁺ in aqueous solution with a detection limit of 1 μM .     

Rhodamine-Appended Bipyridine: XOR and OR Logic Operations Integrated in an Example of Controlled Metal Migration

A new bipyridyl derivative 1 bearing rhodamine B as visible fluorophore was designed, synthesized and characterized as a fluorescent and colorimetric sensor for metal ions. Interaction with Cu²⁺, Zn²⁺, Cd²⁺, Hg⁺, and Hg²⁺ ions was followed by UV/Vis and emission spectroscopy. Upon addition of these metal ions, different colorimetric and fluorescent responses were observed. “Off-on-off” (Cu²⁺, Zn²⁺, and Hg²⁺) and “off-on” (Hg⁺ and Cd²⁺) systems were obtained. Probe 1 was explored to mimic XOR and OR logic operations for the simultaneous detection of Hg⁺–Cu²⁺ and Hg⁺–Zn²⁺ pairs, respectively. DFT calculations were also performed to gain insight into the lowest-energy gas-phase conformation of free receptor 1 as well as the atomistic details of the coordination modes of the various metal ions.     

Multiple-color aggregation-induced emission-based Schiff base sensors for ultrafast dual recognition of Hg2+ and pH integrating Boolean logic operations

Seven Schiff base fluorescent sensors (L¹?L⁷) with multiple-color aggregation-induced emission (AIE) properties for detection of Hg²⁺ ions and pH integrating Boolean logic operations were reported. With appropriate ligand-to-metal coordination (L?HgCl₂) and AIE characteristic, L?HgCl₂ can aggregate into nanoparticles, followed by activation of strong emission, therefore, the “turn-on” assay for detection of Hg²⁺ can be established. Sensing mechanism was calculated through single-crystal X-ray diffraction, Job’s Plot, Benesi?Hildebrand equation, dynamic light scattering, scanning electron microscopy, and elemental mapping analysis. Density functional theory calculations revealed that L?HgCl₂ can avoid one-electron transfer and retain bright luminescence compared with that of L. Different (highest unoccupied orbit) HOMO and (Lowest empty orbit) LUMO energy gaps enable the different electron transitions, resulting in the multiple-color fluorescence properties. Especially, L¹?L⁷ exhibit pH-dependent fluorescent characteristics: different electron-donating ability of the substituent groups for L¹?L⁷ show different titration jump of pH. Advanced level molecular logic gates have been constructed integrating the sensing of Hg²⁺ and pH. More importantly, the L-coated test paper applied in Hg²⁺ sensing makes tracing possible, which is convenient for confidential purposes.     

A colorimetric and fluorescent chemosensor for detection of Hg2+ using counterion exchange of cationic polydiacetylene

In this study, a colorimetric and fluorescent chemosensor for mercury ions (Hg²⁺) was developed. Cationic polydiacetylene (PDA) vesicles with a quaternary ammonium cation and iodide as a counterion show a blue-to-red color transition; the color change is accompanied by a fluorescence enhancement in selective response to Hg²⁺ ions because of a perturbation of the ene–yne conjugated backbone induced by counterion exchange. It allows for selective detection of Hg²⁺ with the naked eye and the sensor is used to determine Hg²⁺ concentrations in tap water samples.     

A rapid selective colorimetric and ‘On–Off’ fluorimetric sensor for detecting Cu2+ ions in aqueous media based on a simple bis-schiff-base derivative

A simple colorimetric and fluorimetric ‘On–Off’ sensor L (3,3′-dimethyl -[1,1′-biphenyl]-4,4′-diyl)bis(azanylylidene)bis(methanylylidene)bis(naphthalen-2-ol) for Cu²⁺ ions bearing o-tolidine substituents has been designed and synthesised, and exhibits significant fluorimetric and colorimetric response for Cu²⁺ in DMSO/H₂O (8:2, v/v) HEPES buffer (pH 7.2) solution. The detection limit of the sensor towards Cu²⁺ is 7.25 × 10^? 8 M and the association constant K_a of 9.86 × 10⁴ M^? 1 was determined. Furthermore, other anions, including Fe³⁺, Hg²⁺, Ag⁺, Ca²⁺, Co²⁺, Ni²⁺, Cd²⁺, Pb²⁺, Zn²⁺, Cr³⁺ and Mg²⁺ have almost no influence on the probe's behaviour. Test strips based on the sensor L were fabricated, which could act as convenient and efficient Cu²⁺ test kits.     

Dual recognition strategy for ultra-sensitive fluorescent detection of Hg2+ at femto-molar level based on aptamer functionalized sulfur quantum dots

In the present study, a dual recognition strategy for ultrasensitive detection of Hg²⁺ was successfully developed for the first time based on aptamer functionalized sulfur quantum dots (Apt-SQDs). The developed Apt-SQDs not only retained the good fluorescence properties of quantum dots but also overcame the problem of poor selectivity of SQDs for heavy metal ions. This system used the dual recognition strategy, including the combination of S_x^2? and Hg²⁺ and T-Hg²⁺-T structures to excellently identify and capture Hg²⁺, and an ultrahigh sensitivity fluorescent aptasensor was fabricated. The fluorescent aptasensor had a good response to Hg²⁺ at concentrations ranging of 10^?15 to 10^?7 M with an ultralow limit of detection of 0.3 fM, and the response to other metal ions was far less than that to Hg²⁺. It was successfully applied to detect Hg²⁺ in nearby environmental water samples (tap water, lake water and river water) with a good recovery rate. Moreover, portable test papers that would be useful for Hg²⁺ monitoring in environmental water were designed. The dual recognition strategy not only achieves ultrasensitive fluorescent detection of Hg²⁺ but also provides a new insight into the further expansion of the application of SQDs.     

A novel rhodamine-based turn-on probe for fluorescent detection of Au3+ and colorimetric detection of Cu2+

In this work, we design and synthesize the novel probe RC through introduction the 1-aza-4,13-dithia-15-crown-5 ring into the structure of rhodamine 6G hydrazide, where the N atom of crown ring is responsible for quenching of rhodamine fluorescence. The compound obtained behaves as multifunctional cation sensor providing selective fluorescent response to Au³⁺ and selective colorimetric response to Cu²⁺ ions in aqueous acetonitrile (1/1, v/v) at pH 7.0. The use of 10^?5?M RC solution allowed reliable determination of target cations in the presence of a wide range of environmentally relevant ions with detection limits of 2?×?10^?6?M and 5?×?10^?7?M for gold and copper, respectively.     

Turn‐on fluorogenic and chromogenic detection of cations in complete water media with poly(N‐vinyl pyrrolidone) bearing rhodamine B derivatives as polymeric chemosensor

A hydrophobic organic monomer GRBE with a polymerizable methacrylester moiety had been synthesized by reaction of rhodamine B‐ethanediamine with glycidyl methacrylate. A water‐soluble polymeric chemosensor poly(VP‐GRBE) had been prepared via copolymerization with a hydrophilic comonomer (vinylpyrrolidone) and GRBE, which was able to sense environmentally poisonous cations in completely aqueous media. The chemosensor was a derivative of rhodamine B, which behaved as a fluorescent and chromogenic sensor toward various heavy cations, particularly Cr³⁺, Fe³⁺, and Hg²⁺. Titration curves of Cr³⁺, Fe³⁺, and Hg²⁺ were constructed using rapid, cheap, and widely available technique of fluorescence spectroscopies. The detection limits for Cr³⁺, Fe³⁺, or Hg²⁺ ions were found to be 2.20 × 10^?12, 2.39 × 10^?12, and 1.11 × 10^?12 mol/l in the same medium, respectively. Moreover, a colorimetric response from the polymeric chemosensor permitted the detection of Cr³⁺, Hg²⁺, or Fe³⁺ by “naked eye” because of the development of a pink or brown yellow color when Cr³⁺, Hg²⁺, or Fe³⁺ cations interacted with the copolymer in aqueous media. Copyright © 2015 John Wiley & Sons, Ltd.